Considerable evidence has accumulated from structural investigation on plasmacytoma proteins, genetic studies on immunoglobulins and cellular events of immunoglobulin biosynthesis which indicates that two discrete genes govern the synthesis of a single immunoglobulin polypeptide chain. In order to gain additonal insight into the genetic mechanism of immunoglobulin formation, we propose to analyze the structure of two gamma heavy chain disease (HCD) proteins. These immunoproteins appear to result from an abnormality of gene expression and could conceivably clarify the process of gene translocation- the fusion of genes responsible for heavy or light chain synthesis, which may be the possible key to understanding immunocyte differentiation. Preliminary studies indicate that one HCD protein exhibits unusual physicochemical and immunochemical properties. Therefore, to understand the possible uniqueness of this protein, we plan a complete chemical characterization, with the ultimate goal of elucidating the primary structure of this molecule. Such results would allow us to define the nature and extent of the presumed molecular deletion occurring in this protein. An additional reason for studying the structrue of gamma HCD proteins is that the genetic defect found in these proteins could be the precipitating factor in the establishment of the malignancy.